Arsenic readily crosses the placenta and is teratogenic in animal models. However, few epidemiologic studies exist on the potential teratogenic effects of arsenic in humans. Scant prior data from the US and emerging data from Bangladesh suggest a link between drinking water arsenic and occurrence of congenital anomalies. We propose to conduct a pilot study integrating geospatial and epidemiological data to characterize the spatial distribution of birth defect occurrence in New England in relation to environmental exposures, in particular inorganic arsenic. In this pilot study: 1) We will quantitatively characterize the spatial distribution of birth defect occurrence and determine the presence of any high-risk areas (i.e., birth defect hot spots); 2) We will quantitatively evaluate spatial associations between birth defect occurrence and water arsenic concentrations; 3) We will conduct a pilot case-control study (as a feasibility study) to investigate at the individual level the associations between birth defect occurrence and arsenic and other environmental exposures. Geocoded data on birth defect occurrences will be made available through the New Hampshire Birth Conditions Program. We will estimate drinking water arsenic exposure using public databases combined with a large data set of private water systems collected through epidemiologic studies in the state in collaboration with the USGS. We will test whether an excess in major and minor birth defects are associated with drinking water arsenic exposure using geographical information systems (GIS) and a specialized software package we designed for a previous study of radon and lung cancer to be extended as part of this pilot study. We will further assess the feasibility of conducting a case-control study of birth defects in the region (i.e., with the collection of individual biomarker data on arsenic), and conduct preliminary analyses of the arsenic-birth defects associations on an individual level. To our knowledge this will be the first attempt of this kind to investigate arsenic exposure and congenital anomalies in a US population.